Blog - AntennaSys, Inc.https://www.antennasys.com/antennasys-blog/Fri, 15 Jun 2018 13:53:28 +0000en-USSite-Server v6.0.0-15104-15104 (http://www.squarespace.com)Anker, AirPods and the Physics of BluetoothSpencer WebbMon, 26 Sep 2016 13:24:11 +0000https://www.antennasys.com/antennasys-blog/2016/9/26/anker-airpods-and-the-physics-of-bluetooth.html5b1040cf4611a06de08de662:5b104802af68497d6a4558cb:5b104802af68497d6a4558e7This is a hands-on product review of the Anker “SoundBuds Sport IE 20”
Bluetooth earphones and a hands-off bashing of the design of upcoming Apple
AirPods. The $30 cost of the Ankers was an experiment, which turned into a
rather useful purchase to accompany my iPhone. I explain why physics is
the limiting factor to the performance of these products. …This is a hands-on product review of the Anker “SoundBuds Sport IE 20” Bluetooth earphones and a hands-off bashing of the design of upcoming Apple AirPods. The $30 cost of the Ankers was an experiment, which turned into a rather useful purchase to accompany my iPhone. I explain why physics is the limiting factor to the performance of these products.

I have been using these $30 Bluetooth headphones now for about 2-3 weeks. The Anker SoundBuds Sport IE 20 was my first Bluetooth device since I abandoned the Jawbone Bluetooth earpiece years ago due to a serious dropout problem; the problem, however, was with PHYSICS and not the product itself (which I otherwise rather liked).

This purchase was fueled by the Apple AirPods announcement. Those jewels will set you back $159 per pair, and the use of the word "pair" is key. Well, it's really three pieces... the two wireless earbuds and the rechargeable charging case.

These Ankers use a cable from USB to some micro connector to charge their batteries. A multi-color LED gives you charging information which is quite simple and useful.

The wire between the two earpieces does more than meets the eye. It distributes audio signals and power, and apparently serves as the antenna. But, the most important use is keeping them around your neck when you pull them out of your ears. The most surprising finding in my experiment: that wire is absolutely necessary to make these ergonomically useful.

The Ankers have a clever feature behind their utilitarian-shaped flat backs: magnets. When you put the backs together, they stick to each other which does two important things. It turns them into a necklace around your neck, which is a very convenient, useful and durable storage position. It also disconnects their power, saving their (very small) batteries when they are not in use. THIS is brilliant design. They don't seem to quite know how to trumpet these features based on the adverts that I have seen, making them a triumph of Engineering over Art. One look at the cinder-block inspired design confirms that Art had left the building.

The Ankers come with a little bag of at least three different sizes of rubber "grommets" for fitting to your ear canal. Then there is some other rubber widgets with horn-shaped protrusions to help keep them in your ear. All of which is user-customizable and optional. I needed to use the large size grommets, and that's it. They work perfectly, sound good, and don't fall out. When all is said and done, there is remaining this little bag of spare rubber parts sitting on your desk. Maybe you'll change your grommet sizes some day, maybe you won't. But, it's a reminder that Anker acknowledged that not everybody's ear is the same shape. Apparently Jony Ive has not.

And then there are the audio dropouts: the annoying loss of connection between your Bluetooth earphones and your audio source. And it’s due to physics, not Anker nor Apple nor Bluetooth per se.

I call it the "Right-Ear Left-Back-Pocket Problem" (RELBaPP). Bluetooth operates on the 2.4 GHz frequency band, which is the same band as WiFi. And microwave ovens. Your body is a very, very good absorber of 2.4 GHz energy. Mostly, it’s because you are a carbon-based bag of salty water. Radio frequency (RF) energy that hits your body will be largely absorbed and turned into heat. Remember that microwave oven? Same deal, it's just that you are not a roast chicken and the heat generated is many, many orders of magnitude smaller.

Radio waves, like light (which are radio waves), want to travel in a straight line. The problem is that the straight line between your right ear and your left rear pocket goes right through a big carbon-based bag of salty water. So, does the path between your right ear and your left ear. Guess where I keep my iPhone. Yep.

So, in three weeks of using the Anker bluetooth headphones, I have had audio dropouts. When I am standing up, walking about my workshop and listening to podcasts, they are infrequent and brief. If I sit at my desk, they are more frequent. Subjectively, however, it’s better than my old Jawbone earpiece which was eventually abandoned due to its dropout behavior. And that MAY be due to the use of the Anker’s connecting wire (or part of it) as the antenna, it’s size making it more efficient than a tiny internal antenna.

(Surprisingly, Dear Reader, this antenna designer will not bore you with an antenna lecture at this time. You’re welcome.)

The Ankers are a keeper. They are useful, convenient, and fill a need for me. I listen to lots of podcasts, and a little music. When I am working in my shop or washing dishes, the lack of wires is welcome. Their sound attenuating design helps in noisy environments. The battery life is adequate, and I am unbothered by the need to plug a cable into them for charging. At $30 for the Ankers, it’s a rather painless purchase.

Enter the Apple AirPods. I’d like to be wrong, but I think they are going to be a disaster.

Their shape appears to be the same as the latest Apple ear buds with the wires cut off. Well, that shape never fit my ears (unlike the previous generations), and there was no solution. So, in my office, in my “Apple Stuff” box, there are multiple copies of those fashionably-designed earbuds in their fashionably-designed plastic boxes, unused. Nobody in my Apple-equipped family uses them. I have friends that echoed the same situation, and Apple has no recompense. If you don’t have a fashionably-designed ear, you can’t use these ear buds. And the AirPods appear to have the same shape with no further solutions offered. Maybe a carefully crafted bit of duct-tape can help you customize your $159 AirPods. How unique they will be!

And when you need to remove your headphones because you are having a conversation with a coworker, what do you do? With my Ankers, I pop one out and let it hang by the wire. Or, take both out and click them together around my neck. The AirPods will need to be shoved in a pocket, or the charger case which you are (additionally) carrying in your pocket. Their size is their liability. (It took fifteen seconds after the product announcement for a company to offer an aftermarket “string” for the AirPods.)

If an AirPod pops out of your ear by accident, it's gone. And at $159 per pair, it’ll be interesting to see what Apple will charge to sell you a single one.

Neither Anker nor Apple can change physics. There’s a lot of salty water between either earpiece and your left back pocket. And between each other. But don’t worry, I am certain that Apple did extensive testing during the RF design of the AirPods. There is no way they would release a product that won’t work as designed around the human body. Between computer simulations, testing with human-body analogs, and beta-testing with real people, you KNOW their product will work insanely great.

And they’re still compatible with your old iPhone 4. As long as you’re holding it right.

]]>Anker, AirPods and the Physics of BluetoothSecurity Flaw in Automotive Keyless EntrySpencer WebbWed, 27 May 2015 15:07:33 +0000https://www.antennasys.com/antennasys-blog/2015/5/27/security-flaw-in-automotive-keyless-entry.html5b1040cf4611a06de08de662:5b104802af68497d6a4558cb:5b104802af68497d6a4558e6Recently there was a security exploit identified in automotive keyless
systems.
Normally, the car sends out an RF ping to the fob on a low frequency, to
which the fob responds on UHF. If the system determines that the fob is
nearby AND a hand is detected by a capacitive sensor, the car unlocks.
Also, if the fob is inside the car AND the ignition button is pressed, the
car will start. Recently there was a security exploit identified in automotive keyless systems.

Normally, the car sends out an RF ping to the fob on a low frequency, to which the fob responds on UHF. If the system determines that the fob is nearby AND a hand is detected by a capacitive sensor, the car unlocks. Also, if the fob is inside the car AND the ignition button is pressed, the car will start.

The fallacy of this system is that signal strength implies distance. The exploit involves amplifying the ping from the car such that the fob will respond even at a large distance. The UHF back-channel is very strong, and needs no further help up to 50 meters away, or so.

Others on the web have described the expolits in detail, but to me, the restaurant scenario is scariest. The perpetrators observe the “mark” going in to a restaurant for dinner after parking his car. Bad Guy A goes in and stands next to the mark with a briefcase. Bad Guy B stands next to the car with another briefcase. Briefcase contains... “electronic stuff”. Open car and burgle. This has been demonstrated.

Steve Gibson covers this and provides pointers to resources at his site HERE, Episode #508.

]]>Design versus EngineeringBreezy Point Update...Spencer WebbMon, 26 Nov 2012 22:57:19 +0000https://www.antennasys.com/antennasys-blog/2012/11/26/breezy-point-update.html5b1040cf4611a06de08de662:5b104802af68497d6a4558cb:5b104802af68497d6a4558e4We left Wayland on Tuesday the 13th....raining, but with two tractor
trailers filled to the brim - the 40' and the 53'!This update from Cynthia Hill... (read original blog entry HERE)

We left Wayland on Tuesday the 13th....raining, but with two tractor trailers filled to the brim - the 40' and the 53'!

We followed the little one and 4 firefighters from Ashby followed the big one to North Haven where we made a driver change - unions !!! Following these trucks thru Queens and Brooklyn was something else!

Our FDNY escort was waiting with lights flashing to take us over the bridge - the Rockaways - to Breezy Point. The sheer number of emergency vehicles was mind blowing, but none belonged to FEMA or the Red Cross!!! Mostly fire and National Guard, back hoes, front end loaders, fire hoses everywhere, and destruction everywhere.

This is a beach community made into a year-round community because fire, EMT's, and police have to live x number of miles from their assigned station and costs were off the wall....so the Rockaway area is now a year-round part of the city. Only problem is that the homes are on slabs or 2-3 foot foundations, and were swept aside by 15' storm surge - BOOM, and they were 100' from where they belonged - one house was split in two, and on the second floor the bed was still made ~ it looked more like tornados mixed with fire and up to 8' of sand left behind.

While the Guard emptied our mother lode, our firefighter Sean took us down to walk the beach....not near the fire, as it's still under a state of emergency, but passed the Army hummers parked on the sand....low tide is over a 1/4 mile from homes and its flat.....you can picture the water coming toward you! We walked for a least a mile, some homes completely not there, just a piece of fence and a house number written in the sand - 206 I remember! Broken everything, everywhere and this was two weeks after the storm...huge piles of stoves, water heaters, car parts, stereos, furniture bits, then a house pretty much intact, but 6' of sand throughout...

No private companies allowed at that point - no water, no gas, no electric, no tools - you could see where everything we brought could and would be used. No insurance people in either...these people felt forgotten, and they had been.

David wants to go back Christmas Eve with nothing but toys, but we need to see what will help them most....kids doing badly as many are still not in school - well they're living there, but no teaching is being done! They are so displaced and sad... all their "things" are gone and you know how much covet their treasures.

Steve, please know that every single thing you and Spencer brought was in good hands within 2 days...everything was gone!

Only thing they don't need is clothing...now I need to know what and when!

Hope you all had the best Thanksgiving.

Big hugs and a ton of thanks.

C.

And more...

This was born yesterday, but we now have a 40 footer to take new toys to Breezy! They have an old traditional Christmas tree lighting that the entire community attends, and celebrates. When I called my civilian liaison, Theresa, yesterday she told me of the party then mentioned they had nothing to give the kids as holiday presents!!!

Their need has been for things to survive, but now it's time to care for the kids!

We are leaving Wayland on Friday, December 14th at 8am...hopefully with the 40' full of gifts, unwrapped.

We placed a maximum amount of $20.00 -$25.00 per gift. We didn't want to see one bike, or an IPhone show up...this way everything will be pretty much equal.

Two things to remember NO SPORTS TEAM LOGOS on sports equipment. These kids have absolutely nothing. NOTHING THAT REQUIRES ELECTRICITY, they have none!

Sports equipment works for all ages from 6 on...they are all very involved in sports. We were even thinking that several of those movable basketball hoops would be great.

You and Spencer were so wonderful with our first load, we'd love it if you could spread the word for this Holiday trip!

Yes, we'll take checks - made payable to Cynthia Hill ~ I'll happily go shopping for these children who have no idea we're coming!

Steve and Spencer, thank you from me and from our Breezy Point friends. They really can't believe people care about them...

Read the attached Letter to the Editor!

Huge hugs,

Cynthia

And a letter to the editor written by Cynthia:

A journey to Breezy Point

To the residents of Wayland, and surrounding communities, the residents of Breezy Point NY, thank you.

They thank you for the two tractor trailer loads filled to the brim with generators, space heaters, work gloves, shovels, 22 wheelbarrows, pallets of bleach, electrical cords, boots, winter clothing for men, women and kids, diapers, pallets of paper towels and toilet paper, antibacterial gel, pet food, and so much more.

You loving brought cars, SUV's, and trucks full of necessities for our neighbors in New York who had nothing left after Hurricane Sandy. Stop & Shop, just days before they opened, not only donated the trucks, but drivers, gas, and their employees to help you unload your car...the General Manager, Mike Bussell, saw people in a horrific mess and along with his corporate team, when to work...he even made sure pallets of drinking water were in both trucks. Mike, also a volunteer Chief with the Ashby Fire Department, knew what these people needed after water, fire and up to 6 feet of sand swept away part or all of their homes.

I wish you could have seen the faces of the FDNY, National Guard and civilian volunteers as those huge trucks pulled in to an area still under a State of Emergency...we lifted the doors and people started to cry. With destruction everywhere they couldn't believe people cared about them....

A woman came up to me and told me I was her angel - I'm sure a few in town would disagree - now she could begin to dig out her house. I certainly wasn't her angel but I could hug her and let her know that so many wonderful people cared what happened to her, that we'd be there for Breezy.

The people of Breezy Point are a strong, proud and caring community, but looking around me, I couldn't imagine what courage it would take to keep going day after day.

It's been almost a month now ~ Breezy still has no electricity and all must leave before dark. You've probably heard about the looting, Theresa tells me it's not too bad. What do you mean "not too bad" I shouted to myself, you've worked for days to find odds and ends of your life, and someone steals it!

As the sun set on Breezy Point, November 13th 2012, several of us knew we'd be back, with whatever they needed, whenever they needed it.

Thank you for all that you've done, and all that we have left to do.

Cynthia Hill, the Breezy Point Project

]]>Breezy Point Update...A pictoral history of cell phones...Spencer WebbMon, 19 Nov 2012 22:58:54 +0000https://www.antennasys.com/antennasys-blog/2012/11/19/a-pictoral-history-of-cell-phones.html5b1040cf4611a06de08de662:5b104802af68497d6a4558cb:5b104802af68497d6a4558e3Please check out an excellent graphical history of the cell phone entitled
"evolution of the mobile phone by docomo". Watch for when all the antennas
become internal.Please check out an excellent graphical history of the cell phone entitled "evolution of the mobile phone by docomo". Watch for when all the antennas become internal.]]>A pictoral history of cell phones...Helping Breezy Point...Spencer WebbSat, 10 Nov 2012 21:56:27 +0000https://www.antennasys.com/antennasys-blog/2012/11/10/helping-breezy-point.html5b1040cf4611a06de08de662:5b104802af68497d6a4558cb:5b104802af68497d6a4558e2I recieved a note from my friend Steve Golson about a donation drive for
victims of Superstorm Sandy in Breezy Point, NY.I recieved a note from my friend Steve Golson about a donation drive for vicitms of Superstorm Sandy in Breezy Point, NY. I grew up in Coney Island, Brooklyn, NYC, and when you looked out across the water (I lived on the 12th floor of a 23-story apartment building) you would see Sandy Hook NJ on the right and Breezy Point on the left. Pictures of my old neighborhood in Coney Island were stunning in their depiction of the damage from the storm. So, when I had the opportunity to do something to help I volunteered AntennaSys' resources.

Steve send me a link to an article about his friend and travel agent Cynthia Hill. Cynthia knows some firefighters who live in Breezy Point and work in Manhattan. She organized a drive for items that were sorely needed in the recovery efforts, got the Stop-and-Shop supermarket chain to donate trucks, and got locals firefighters to help with loading efforts in Wayland MA.

Of all the available AntennaSys resources, the most important for this mission were three: a credit card, an enclosed trailer (which we use to transport equipment and supplies for the courses we teach) and cheap labor. These were immediately pressed into service. With a shopping list in hand, and additional text messages relayed to me from Cynthia via Steve, my daughter Samantha and I headed to Cyr Lumber to load up.

As keeper of the list, Samantha made sure we got the highest priority items. We were time-limited and needed to be on the road at 2pm in order to make the drop.

Cynthia not only got Stop-and-Shop to donate trucks, but these trucks were staged in the brand-new parking lot of a supermarket that was not yet open.

What an amazing operation. We were unloaded in four minutes and watched one of TWO 40-foot trailers hit it's limit.

Best of luck Breezy Point. Thank you Cynthia, Stop-and-Shop, and the Firefighters.

Windmill International, Inc. announced that it has received a $9 million order for their KA-10 Suitcase Portable Receive Suite (SPRS) for Central Command Special Forces in Afghanistan. The order included KA-10s, training, and product support. Windmill's KA-10 SPRS is a highly-portable, rugged satellite receiver system developed to support Special Operations forces deployed overseas. The battle-ready KA-10 conveniently brings crucial command center information and data to the in-field warfighter, substantially improving mission success probabilities and saving lives. [...more]

In September of 2004, Mr. David Martin (Windmill International, Inc.) and I, along with our AFRL sponsor Mr. John Turtle briefed the Special Operations Command on the results of our SBIR Phase I and Phase II program. The briefing was entitled "AFRL SBIR contract to develop lightweight GBS Rx antenna for Special Forces". The press release above is the culmination of that briefing and the result of hard work by a fantastic engineering team that simply did not understand that it couldn't be done.

Dave Martin (R) and myself (L) at Wahiawa, HI demonstrating the "Iron Maiden" in July 2004

In the picture above, our prototype weighed 65 lbs., but replaced about 400 lbs. of equipment, and ran on batteries. The then-current system is shown in the background; it is a 1-meter dish antenna. The "Iron Maiden" was the precursor of the new KA-10 system which weighs about 40 lbs.

The working prototype KA-10, with Dave and I on our way to a demo in Washington DC, December 2005

The original goal of the system was to be sized for airline carry-on. It struck us that we had achieved our goal when we were on a commuter jet bound for DC from Manchester NH. (Photo by Dave Martin)

Upon arriving at Dulles, we were reminded by the Arrivals Board that while the hardware may be working perfectly, there were things that could still go wrong. One challenge was that it was FREEZING in DC when we got there, and had to go to the mall to buy thermal underwear for the demo. We demonstrated the unit on Pearl Harbor Day, December 7th, 2006.

The system worked perfectly, though the demo gremlins were quite active. We had overcome magnetic anomolies, loose hardware, and a temperature-related sensor failure. All these things were taken back to the engineering team as lessons learned and made the ultimate product better. And, yes, we blamed some problems on software... unfairly. Sorry, Dan.

There are many, many people to thank for having worked on this project, and I have not asked any of them permission to use their names. But to them I say THANK YOU!! It's been a wild ride.

At MILCOM 2006

(U.S. Patent 7,889,144 and other U.S. and International Patents both issued and pending.)

]]>An SBIR Success Story and a Win for the Warfighter!AntennuatorsSpencer WebbFri, 12 Aug 2011 20:24:46 +0000https://www.antennasys.com/antennasys-blog/2011/8/12/antennuators.html5b1040cf4611a06de08de662:5b104802af68497d6a4558cb:5b104802af68497d6a4558e0You can't win.
You can't break even.
You can't even get out of the game.
And playing the game is not optional.You can't win.You can't break even.You can't even get out of the game.

Breaking the laws of physics is a popular pastime. Who would not want to get a thousand miles per gallon, lose weight by taking a pill, or receive a fortune in cash from a Nigerian prince by email? But, most of us understand it just ain't going to happen. And so it is with antennas. Previously, I wrote about the tradeoffs associated with antennas. The most contentious corner of our tradeoff triangle seems to be size; it's the easiest to measure, and the one in most visible conflict with other aspects of wireless product design.

You want your antenna small, admit it.

Small antennas have been around a long time. Remember pagers? They most often operated in the VHF band, where wavelengths were on the order of two meters. Yet, they were tiny (although the volume of cell phones is approaching what later model pagers were) and the antennas they contained were even tinier. The facts that enabled their good performance were: narrow frequency range and receive-only operation. You can have small size if you give up bandwidth and efficiency. No problem. For many years, AM radios operated from 510-1800 KHz (with wavelengths in the hundreds of meters) using a ferrite loopstick at the core of their antenna; narrow bandwidth, low efficiency, and completely successful.

But, these days who wants to give up bandwidth? If size is the easiest thing to measure, then impedance bandwidth is a close second. An RF network analyzer can measure impedance bandwidth in a few milliseconds, and generate a curve which can be put in a data sheet, or used to compare to an existing data sheet. So, let's make a small antenna with wide bandwidth!! If we're lucky, nobody will ask about the efficiency (which is pretty hard to measure, but easy to experience).

And so, some companies manufacture Antennuators. These are a cross between antennas and attenuators. Between good and evil. Between protein and carbohydrates. Between Apple and Microsoft. Let's radiate some energy and burn some energy as heat. That way, it's kind of usable, and the measured impedance bandwidth is glorious!

There are several ways to build an Antennuator. The easiest method is to build it with lossy materials in the parts that carry RF current. One example of such a material is stainless steel. Stainless steel is a rather poor conductor, but its nice to look at and resists corrosion. There are many whip antenna made from stainless steel, and often the environmental considerations outweigh the loss from the material selection. And in certain antenna types, which are inherently high impedance (such as the Kraus Helical) the difference in material losses will be insubstantial. But, when antennas are made physically small the currents can get rather high, and this is where lossy materials will rear their ugly head.

A few years ago I was working for a company that manufactured various specialized receivers and transmitters operating in the VHF, UHF and low-microwave range. I was the in-house antenna engineer as well as a product designer. A good friend of mine, John D., came to my office with a question. He ran the test department which had the responsibility of tuning and testing all the equipment before shipment. A group of "tactical repeaters" were being tested, and one was on his bench transmitting a few watts of RF at VHF into a six- or eight-inch "rubber duck" antenna (a helically wound short monopole).

"Spence, should the antennas get warm?"

I turned and looked at him incredulously. After careful consideration I answered with a incisive question of my own, "HUH?!!?"

"After about five minutes the antenna is warm, and I don't remember this happening before. Is it normal?" John asked.

"Hell, no!" was my measured response which began a careful investigation into this Antennuator.

I verified that, indeed, the antenna was warming up substantially, and that it was not some other portion of the system making heat and warming up the antenna. After some digging, John and I determined that there was a recent vendor change from vendor "C" to vendor "A". I grabbed some examples of the parts from each vendor and started cutting them open (this is a recurring theme, as you will see, Dear Reader). The helical conductor from vendor "C" was copper-colored, and that from vendor "A" was stainless-steel colored. Hmmmm.

Then I took scraps of the plastic that encased each antenna and carefully tested the dielectric loss using an UHF RF Thermal Conversion Exposure Cavity. Yep. . . a microwave oven. The difference in thermal dissapation between the two plastics was very significant: after about 15-20 seconds of exposure (with a cup of water at the opposite corner of the microwave for loading) the plastic from vendor "A" got hot whereas that from vendor "C" was not noticably warmer -- lossy dielectric confirmed. (While this test was conducted at about 2450 MHz, it is still indicative of losses at VHF.)

The Antennuator from vendor "A" looked great on the RF network analyzer, and even better in the purchasing department's scorecard. But, it was burning precious (battery powered) RF in the process. I immediately wrote an ECO (Engineering Change Order) eliminating vendor "A" as a supplier, and specifically naming vendor "C" as the supplier for this particular part. Problem solved. Purchasing had been credited for saving money on cheaper antennas, and Engineering looks evil throwing out inventory. The Earth continued turning on its axis.

More recently, one of my clients brought me a product from a Serious Defense Contractor, which was labelled "Antenna, Broadband, 50-2000 MHz". It was about twelve inches long, about 5/8-inch in diameter, with a BNC male connector on one end. It was flexible, black, and no doubt expensive. Since my client was taking a training class, I immediately used it as an example of an Antennuator. I started a discussion with the class as to how a twelve-inch long antenna can be rated for operation from 50-2000 MHz. After a healthy amount of discussion, one of the students put the antenna on an RF network analyzer and swept it from 50-2000 MHz, measuring the input impedance.

"It looks good to me!" he said, showing a respectable "knot" in the middle of the Smith Chart, indicating a VSWR of less than about 2:1 (ref. 50-ohms) over the range.

I said, "You'd think so, but remember the engineering rule: if you can't fix it, at least you can break it!". I extended the low end of the measurement down to 2 MHz. And do you know what we saw? It still had a VSWR of about 2:1. . . . but, it shouldn't have. It SHOULD have looked lousy at 2 MHz. Now think, what has a VSWR of 2:1 at 2-, 50- and 2000-MHz? That's right -- a RESISTOR!

I made a bold (and risky) statement to the class: "There's a 100-ohm resistor in parallel with the connector.", I confidently proclaimed, hoping like hell nobody would call me on it. Well, I was with a group that did not see any impediment to cutting open the antenna and finding out Right Now. And so, they did.

I was wrong. There were two, 200-ohm resistors (each rated 3-watts) in parallel across the connector. As I see it, when RF current flows in a conductor the only thing it can make is radiation, but when RF current flows in a resistor the only thing it can make is heat. So, the ONLY possible reasons those resistors were there were to make the transmitter happy over that frequecy range (no spurious oscillation, no VSWR alarms), to make the datasheet look magnificent (and meet procurement requirements), or to prevent the buildup of ice. Unfortunately, my clients are professional communicators and in need of their equipment actually... you know... communicating, and they were already acutely aware of the inefficiency of this product. Putting "50-2000 MHz" on the body of an antenna does not make it so. Notice the efficiency was not stated on the same placard. Pity.

Once I designed an antenna for a small surveillance product that had a resistor in it. The product was battery operated, and had a very high efficiency transmitter. Sometimes, however, if the antenna came too close to a conductor, it presented the transmitter with a very low impedance that caused a spurious oscillation. This was Very Bad in the intended application. I ended up using a small series resistor in the feed loop of the electrically small loop antenna. The cost of this resistor was a fraction of a dB of transmitted signal in normal operation, but it prevented the spurious oscillation completely and the associated loss of signal. This was a carefully weighed decision, it solved the problem, and the efficiency cost was calculated and acceptable. The problem could have been solved further upstream in the power amplifier, and there would have been an efficiency cost there, too.

Resistors turn current into heat. That's what they're supposed to do, and thank goodness they do it so well. But, when you find 'em in antennas, it's worth asking why they're there.

Sometimes, it's useful to burn undesired energy of the wrong polarization as in a Terminated Bifilar Antenna or a Log Spiral Antenna, for example. In that case, polarization purity (axial ratio) is more valuable than efficiency. That is an engineering decision, and a good one.

Sometimes, it's critical to keep the transmitter happy and invest in a bit of heat to do so.

Sometimes, it's to make the datasheet look miraculous and score a big order from the government.

Perhaps someone should ask the professional communicators if the solution to their very real problems is an Antennuator. I think not.

]]>AntennuatorsThe Antenna Tradeoff TriangleSpencer WebbSat, 30 Jul 2011 18:33:00 +0000https://www.antennasys.com/antennasys-blog/2011/7/30/the-antenna-tradeoff-triangle.html5b1040cf4611a06de08de662:5b104802af68497d6a4558cb:5b104802af68497d6a4558dfEvery professional pursuit has its tradeoffs which must be managed. In
fact, I believe that it is the principal function of the engineer to manage
tradeoffs.Dusty sign seen on the wall in Ye Olde Machine Shop:

You can have it:

Fast Accurate Cheap

Pick any two.

Every professional pursuit has its tradeoffs which must be managed. In fact, I believe that it is the principal function of the engineer to manage tradeoffs. We want airplanes to be strong, but light and affordable. We want our favorite restaurant to be inexpensive, tasty and prompt. We want our politicians to be honest, responsive and effective (OK... it's just theoretical). These competing desires are what we call the Tradeoff Triangle. Sometimes the number of parameters we need to balance exceeds three, but for the purposes of our discussion today, the number shall be three... no more, no less. Three shall be the number of thine tradeoffs, and the number of the tradeoffs shall be three. Four shalt thou not consider, neither ponder thou two, excepting that thou then proceed to three. Five is right out.

But, I digress.

Let's explore what the job of an antenna is, and where its tradeoffs can be found and thence managed. And we are going to assume that antennas are reciprocal. That means they can make radiation from RF current (transmitting), and they can make RF current from radiation (receiving). In any wireless device, there is a receiver section, a transmitter section or both (transceiver). These functional blocks are designed by a clever and talented RF guy, and generally interface to the antenna via a transmission line of a certain characteristic impedance; the most familiar values for this impedance are 50- and 75-ohms. (The reason for the existance of these two values is a good subject for a future blog entry. Anyone know the history of these choices?)

Usually, I hate it when someone tells me the punchline before I hear the joke. Sorry, but here it is: Your antenna can be wideband, small or efficient. BANDWIDTH, SIZE, EFFICIENCY. Pick any two. It is a sure sign of Antenna Snake Oil when you see tiny, wideband antennas boasting ultra-high efficiency. Run the other way. OK, let's take a closer look...

Antennas operate over limited bands of frequencies. Sometimes these bands are smaller than we wish they were. A useful way to think about bandwidths is called "fractional bandwidth" (FBW); for our purposes we'll define fractional bandwidth as the high frequency divided by the low frequency.

For example, modern cell phones generally require antennas that operate from 806 to 915 MHz (FBW=1.14 or 14%) AND 1710 to 1990 MHz (FBW=1.17 or 17%). This covers all the GSM bands as well as the PCS bands. Another familiar band is the 2.4 GHz ISM band which is where WiFi lives; this band is 2.4 to 2.5 GHz (FBW=1.04 or 4%). Yet another example is the 900 MHz ISM band which is often used for wireless phones and other household and office devices; this band is 902 to 928 MHz (FBW=1.03 or 3%). And finally, we are all familiar with GPS which needs about 10 MHz of bandwidth centered around 1575 MHz (FBW=1.006 or less than 1%).

So, antennas for each of these applications need to operate over the entirety of these bands. This property, which is the first of our three tradeoffs is loosely called BANDWIDTH. In the four examples above, note that the fractional bandwidth is representative of how "hard" it is to meet this requirement in light of our (soon to be illuminated) other tradeoffs. GPS seems easy, and "Quad Band GSM" seems hard. And so they are.

Now, using the term "bandwidth" without any further qualification is Engineering Blasphemy (see also my rants about the use of "dB" without a reference). The bandwidth of an antenna is completely dependent upon what is relevant to the application. For cellphone applications, it may be the "efficiency bandwidth" or that bandwidth over which the total radiated power (TRP) or the total isotropic sensitivity (TIS) is north of a required value. For GPS we may be bandwidth-limited by the axial ratio, or the quality of the circular polarization (RHCP in the case of GPS).

Frequently, the bandwidth of concern is the impedance bandwidth, which is the bandwidth over which the antenna's impedance remains within a certain "distance" (on the Smith Chart) of the ideal impedance. Often this is expressed as Return Loss (10 dB is the usual minimum value), or VSWR (Voltage Standing Wave Ratio) where 2:1 is the usual limit. If someone uses the term "antenna bandwidth" without explicity saying which bandwidth they are referring to, it is probably the impedance bandwith. And thereafter they shall be scolded.

The second tradeoff in our triangle is SIZE. There's different ways to think about size. You care about physical size when you are trying to stuff ten pounds of stuff in a five pound bag: you want your consumer product to be as small as possible and the industrial designer has graciously given you a volume which would not host most DNA molecules. The antenna designer is thinking in terms of wavelengths. As the antenna volume starts becoming a smaller and smaller fraction of a wavelength, the impedance bandwidth starts shrinking, and the ability to remain efficient with real-world materials starts disappearing.

In December 1948, Lan Jen Chu published the paper "Physical Limitations of Omni-Directional Antennas", in which he derived a theoretical formula of the bandwidth of an electrically-small antenna. In the interest of circumnavigating a soporific vortex, the conclusion is thus: the smaller the antenna, the narrower the bandwidth. So there.

EFFICIENCY is the measure of how much of your RF power is going to be radiated, and how much is going to be turned into heat. Assuming your goal is not de-icing, heat is an undesireable byproduct. With real-world materials, especially as we shrink antennas, this becomes a significant concern. A side-effect of shrinking the antenna is causing the antenna's RF currents to become large enough to make the radiation happen. These high currents make the material losses which were previously ignorable a very real concern. I have designed electrically-small loop antennas which have a radiation resistance (the good "resistance") measured in milliohms. Suddenly the fact that the conductor is copper as opposed to aluminum becomes really important. The dielectric materials used in trimmer and fixed capacitors for resonating such antennas become critical.

While it is pretty clear that losses in conductors and dielectrics are undesireable from an efficiency standpoint, there lurks in the shadows a side effect as enticing as it is detrimental. These efficiency-robbing losses make the impedance bandwidth appear larger. In fact, the higher the losses the wider the impedance bandwidth until the limit where ALL the energy is dissipated in losses and the bandwidth seems "infinite". The ultimate example is a 50-ohm terminator: a perfect match over a huge bandwidth... and zero radiation. The Dummy-Load Antenna. The lesson is clear: When presented with an antenna with unexpectedly large bandwidth for its size, ask about the efficiency. Oftentimes, this line of questioning is met with a stunned silence at best, or a complete change of topic at worst. There is a tiny fraction of antenna companies operating today whose business plans depend upon your failing to inquire about efficiency. I'll say it again: About the Efficiency - Ask!

The product designer, antenna designer, industrial designer and marketing professional together must all cooperatively grapple with the antenna tradeoff triangle: BANDWIDTH, SIZE, EFFICIENCY.

Like it or not... Pick two.

]]>The Antenna Tradeoff TriangleDemystifying AntennasSpencer WebbFri, 22 Jul 2011 21:21:10 +0000https://www.antennasys.com/antennasys-blog/2011/7/22/demystifying-antennas.html5b1040cf4611a06de08de662:5b104802af68497d6a4558cb:5b104802af68497d6a4558de﻿Since my last blog post I have been working on multiple projects with
multiple, wonderful clients.﻿Since my last blog post I have been working on multiple projects with multiple, wonderful clients.

Most significantly, I taught a training course on antennas over the course of two weeks. Eighty hours of training. If you've ever done training, that may sound exhausting. And you'd be right. But, boy, was it rewarding!

Getting opportunities to teach what I have been learning over the last sixteen years is, for me, a lot of fun. I have trained groups from the commercial, government and law-enforcement arenas. The topic of antennas is often intimidating for those that use them, but don't design them. It's seen as super-technical and borderline black-magic. Perhaps it's because RF and antennas seem to the uninitiated what Einstein called "spukhafte Fernwirkung" or "spooky action at a distance". You can't see it, but it works. As one antenna guy put it, "If RF was visible, we'd be out of business."

So, in order to train people how antennas work, you have to make the RF visible. And for two weeks, that's what we did.

We started with some physical demonstrations which explain how the dipole antenna works; and we make the claim that the dipole is the simplest resonant antenna you can construct. We spend some quality time watching water slosh back and forth in carefully constructed clear tubes. Then, once people have spent time developing a mental model for how the electrons slosh back and forth in a dipole (and have personally done the sloshing), they "get" resonance, radiation, and even impedance.

Next we get out a telescoping dipole antenna. The very same one we use as a standard in the AntennaSys lab. Add an RF network analyzer, a video projector and the strategic "laying on of the hands" and you have the next "ah-hah!" moment. The students start connecting their simplified physical analogy to the actual electrical system they are playing with. They can't see the electrons "sloshing", but now they believe it's happening based upon the real-time information the network analyzer is giving them. Now, they start believing they can maybe understand a little of this stuff.

Then we predict what would happen if we.....

shorten the antenna,

lengthen the antenna,

feed the antenna at a point offset from the center...

And then we back up their predictions and observations with computer simulations that introduce color-coded graphics which further confirm their observations.

Finally, we started actually building antennas. Everyone in the class made their own dipole. All materials came from the hardware store. Everyone communicated over radios between their hand-made dipoles.

When you take a person from the "antenna as mysterious object" phase to the "it's all about getting the slosh right", you've created a better antenna user, a better product engineer, a better systems engineer, a better communications professional.

And the spukhafte Fernwirkung ain't quite as spooky as it was.

(Thank you Steve and Corinne for helping AntennaSys deliver a great course. A special THANK YOU to Agilentand Anritsu for providing the RF Network Analyzers used in my course!)

]]>Demystifying AntennasIs the Verizon iPhone antenna fixed?Spencer WebbThu, 13 Jan 2011 21:28:47 +0000https://www.antennasys.com/antennasys-blog/2011/1/13/is-the-verizon-iphone-antenna-fixed.html5b1040cf4611a06de08de662:5b104802af68497d6a4558cb:5b104802af68497d6a4558ddThe SIM slot is gone, since it's not a GSM phone. That frees up a bunch of
real estate on the PC Board. Did Apple move the WiFi antenna (and probably
also the GPS antenna) to the PC Board, under the rear glass? The SIM slot is gone, since it's not a GSM phone. That frees up a bunch of real estate on the PC Board. Did Apple move the WiFi antenna (and probably also the GPS antenna) to the PC Board, under the rear glass? I think so.

In their FCC filing, Apple describes the WiFi antenna as a "PIFA". This stands for Planar Inverted-F Antenna. I would never describe the "frame" antenna using those terms. So, this seems to support the theory. Further, the photos (thanks to Arstechnica) of the new Verizon iPhone show elimination of the frame gap on top (which was the WiFi and GPS antenna) and creation of new gaps on the sides.

Is the new iPhone using antenna diversity (two antennas in the frame with switching between them) to compensate for hand effects? Possibly.

Stay tuned.

(thanks to Greg Keizer of Computer World for sending me the link to the photos.)

]]>Is the Verizon iPhone antenna fixed?Product Data Sheets AvailableSpencer WebbThu, 18 Nov 2010 19:55:41 +0000https://www.antennasys.com/antennasys-blog/2010/11/18/product-data-sheets-available.html5b1040cf4611a06de08de662:5b104802af68497d6a4558cb:5b104802af68497d6a4558dcToday I posted two data sheets for products that we have been making for
clients. They have many applications and can be scaled to other frequency
ranges.Today I posted two data sheets for products that we have been making for clients. They have many applications and can be scaled to other frequency ranges. Have a look in the "Product Data Sheets" section. Let me know if you have any questions.

-SW

]]>Product Data Sheets AvailableApple Does the Right ThingSpencer WebbFri, 16 Jul 2010 17:52:05 +0000https://www.antennasys.com/antennasys-blog/2010/7/16/apple-does-the-right-thing.html5b1040cf4611a06de08de662:5b104802af68497d6a4558cb:5b104802af68497d6a4558dbWhat we will do: iOS 4.0.1 fixes bars. And a free case for everyone. Refund
if you already bought one..."What we will do: iOS 4.0.1 fixes bars. And a free case for everyone. Refund if you already bought one..."

Thank you, Apple.

]]>Apple Does the Right ThingiPhone 4 Meets The GripOfDeathInatorSpencer WebbThu, 15 Jul 2010 03:55:00 +0000https://www.antennasys.com/antennasys-blog/2010/7/14/iphone-4-meets-the-gripofdeathinator.html5b1040cf4611a06de08de662:5b104802af68497d6a4558cb:5b104802af68497d6a4558da“dude, where's the blogs? are you on vacation?" -David O. "dude, where's
the blogs? are you on vacation?" -David O."dude, where's the blogs? are you on vacation?" -David O.

The email, tweets and calls I have been receiving have been voluminous. Both from the extremely positive responses to the previous posts, and those folks anxiously awaiting results of the more detailed tests that we promised. I should say up front that I wish we could have spent more time on these tests, but the reality is that it takes WAY more time to make careful measurements than we care to admit, and more than anyone really believes (including Consumer Reports, apparently). Alas, we will finally report on our foray into quantifying the quagmire.

First a couple of items of administrivia. I read every email I receive. I generally have not responded individually due to lack of time and the demands of my business. However, I am planning on my next blog entry to be the first in a series of "Mailbag Editions", where I will try to answer the answerable emails. You, Dear Reader, are the best source of ideas for this blog and I truly appreciate your input and insight. If you email me, I may use quotes from your email, but I won't use your personal information. If you send me a "mention" on Twitter, however, I may quote it verbatim since you already broadcast it to the world. Please use email to contact me in lieu of a phone call. I actually had someone call me today to ask me if he should buy an iPhone 4. If you are a member of the press, or a blogger, or a podcaster, I promise to do my best to get back to you and answer your questions; but, check this space first for my thoughts and information.

Steve Golson, the lab notebook and the GripOfDeathInator

On to our testing of the iPhone 4. In order to do this right, I needed some help, and not just any help. I needed another nerd engineer. Steve Golson was that unwitting volunteer. I'm implying that he didn't know what he was getting himself into, but seeing as he and I have been friends for about a third of a century, I'm guessing he knew precisely what he was in for. And he got it. In spades.

A bit about Steve. An accomplished VLSI design engineer and consultant, he was the manager of the MIT Rifle Team when I was the manager of the MIT Pistol Team back in the 80's when fast microprocessors had 1MHz clocks and antennas were obvious. Steve and his wife Terry created Hencam.com, and Terry is a wonderful chef and author. Terry released Steve for the day (and night) to accomplish this bit of engineering hacking, and for that I thank her. Without Steve, the GripOfDeathInator would not have been born.

We needed a way to hold an iPhone 4 (or any hand-held device, for that matter) in a way that did not introduce any significant conductive surfaces into its environment, and at the same time allowed a human hand to grip it in a repeatable way. We chose to work in an "open field" environment, with real cell signals. The absolute position of the device under test had be constant, so the relationship of the phone to the cellsite remained uniform. These requirements gave birth to the GripOfDeathInator, pictured above. And that is Steve beginning testing.

The GripOfDeathInator is built from one-inch thick foam sheet. It's glued together with a foam-friendly adhesive from Liquid Nails; thanks to the smart Home Depot guy for that one. The foam is pretty much RF-invisible, but it is strong enough to securely clamp our test devices. I'd love to tell you all the details of the extensive mechanical engineering that went into the design, but really, we winged it. It works as good as it looks. We also found all-plastic saw-horses to create our work table, and a wooden stool for our bag of salty water...um... Steve.

Once we had a way to repeatably position and grip the iPhone, we needed a way to measure the effect of the different grips. The "bars" are useless; we were stunned to find out that we have no idea what they mean, nor what their time constant was. Truly stunned. So, we decided to use the 3G data download and upload speeds. These measurements were made by using the Speedtest.net app. We had very fine-grained measurements of data rate, and indirectly these were telling us about the bit error rate (BER). The BER in turn tells us about the signal-to-noise ratio in the receiver, and the phone's transmitter power received at the cell site; both of these are affected by antenna performance. After much consideration, we decided this was the best way to accomplish the measurement without ripping an iPhone 4 open and firing up the soldering iron... and the microscope. As a result of separately measuring upload and download rates, we discovered that there was a couple of surprises waiting for us as you will see. Each measurement we report was the average of at least five consecutive runs; we also report the spread of those runs to show some indication of the measurement quality.

We also experimented with the azimuthal position of the phone: which direction it was facing. After making a bunch of test runs we decided it was not a significant improvement to include all the points of the compass. However, had we not explored that, we would not have discovered another interesting aspect of our measurement procedure: data rate throttling. You see, Steve was very smart in suggesting that as we tested at the four points of the compass, we rotate the apparatus back to the original position and do a fifth run. This would verify the consistency of our measurements. It was during one of these repeat runs that we observed a drop in the data rate of the download by a factor of 3-4. It lasted about 15 minutes, and things returned to normal. Additional details of this behavior will be the subject of a future blog entry. Has anyone else observed this behavior?

The VIP

The Half-GripWe developed four grip conditions: None, The Vulcan iPhone Pinch (VIP), The Half-Grip, and The Full-Grip. When the phone was not gripped, the operator (Steve) stayed in position and rested the gripping hand on the lower "C" cut in the foam. This insured that the local environment around the phone remained the same. We also kept any metal about 20 feet away or more, and kept it constant through the data runs.

As we were testing, the VIP appeared to be about the same as no grip at all. But, after crunching the data we were surprised to learn that it seemed to have a slight benefit. This could be explained several ways, and was less shocking than it was amusing.

The Half-Grip and the Full-Grip had negative impacts on the data rate that were sensible: the Half-Grip was bad and the Full-Grip was worse.

The Full-Grip

Overview of our test range showing the control phone to the left

After the data-throttling observation, we decided to set up a control phone to observe the network performance as a whole. We reasoned that should the network slow down (as had been observed) we could normalize the data using the control unit's rate measurement. We were wrong. The data throttling was IP address specific. When we had the control phone set up, we observed normal data rates on it when the other phone dropped by 3-4X. Fortunately, the drop in data rate during those periods was so precipitous, that we were able to remove any affected data points easily. More on that in a future post.

Before we get into the data, I should discuss one major limitation of our technique. We could not control the signal strength of the cell tower. We had to take what we got. The good news is that is was a "moderately good" signal; we did not have a cell tower looming over us. Nor did we have a very weak signal that would be easy to completely obliterate. We were illuminated by one cell site only, eliminating the possibility of switching between sites.

This limitation meant that once we observed a condition with good performance, it was hard to differentiate it from another condition with good performance; in other words, the data rates hit their upper limits. We could have used RF absorber material, or moved locations to reduce the signal level, but we really do have wives and kids and like to see them every now and then.

In graphical form, here are our results, below. We are reporting the average (the little box), and the spread (the little "T" bars) of the data rate measurements for both download (red) and upload (blue). Note that the vertical scale is logarithmic, which means that a change in height of the data represents a constant factor (or percentage) regardless of where it is on the graph. The shape of the "curves" is the most important thing to observe since the absolute data rates may still be broadly dependent on network loads.

We can make several interesting observations.

1) Gripping the Naked iPhone 4 certainly had a strong negative effect on the data rates, both upload and download.

2) The effect of the grips on the iPhone 3G is much smaller. But, the Full-Grip still reduces the data rate on upload.

3) Use of the Apple "Bumpers" has a very positive effect on performance. It mitigates much of the effect of the grips at our signal strength level.

5) There was a large spread in the data during the Full-Grip, in both upload and download. This highlights the sensitivity of the antenna design to direct contact by the hand.

In plain terms, the iPhone 4 SmartModule becomes a SmartPhone with the Bumpers.

What about the Consumer Reports "Duct Tape" fix? Yep, it will help. Any insulator over the "gap" area of the antenna is going to help in direct proportion to its thickness. I think Consumer Reports was going for style points in the selection of Duct Tape. Nice move - they sure dominated the news cycle.

But, hey, Consumer Reports guys: you don't do radiated tests in a shield room. That's like measuring the light output of a desk lamp in a house of mirrors. It's amateur hour. Either you didn't really explain your experimental technique fully in your video and text on your website, or perhaps you did and it really stinks. In either case, we end up agreeing with each other, so let's not dwell on that too much.

I have had the Apple Bumpers on my iPhone 4 now for about a week, and have been putting it through its paces. It does fine. I will probably get an Otter Box case when they come out (provided there are no gotchas). I cannot imagine owning this phone with no case. And I can't imagine not owning an iPhone; it's a great device.

However.... Apple: you really need to give every iPhone 4 owner a free bumper. We've proven it really helps reduce the hand sensitivity problem. And it became a problem the minute one of your employees said to a user, "You're holding it wrong." Instantly, you established that there was a right way and a wrong way to hold it. Surely, if we review our manual for the iPhone 4 we'll discover that .... oh wait .... there is no manual. And the pamphlet that comes with it says absolutely NOTHING about how to hold it. Despite its ironic title: "Finger Tips".

Apple, give everyone a bumper. And give me my twenty nine bucks back for the one I bought.

Or, just buy me sushi and we'll call it even.

]]>iPhone 4 Meets The GripOfDeathInatorThe iPhone 4 SmartModuleSpencer WebbWed, 07 Jul 2010 18:24:41 +0000https://www.antennasys.com/antennasys-blog/2010/7/7/the-iphone-4-smartmodule.html5b1040cf4611a06de08de662:5b104802af68497d6a4558cb:5b104802af68497d6a4558d9Apple has produced the world's first and best SmartModule. It's called the
iPhone 4.Apple has produced the world's first and best SmartModule. It's called the iPhone 4.

Let me explain.

I enjoy photography, and have had a professional-grade Nikon SLR in my hands since I was about 13. When you buy a camera like that, you really aren't buying a camera. You seperately purchase the body, the lens, a more comfortable strap, perhaps a corrective eyepiece or even a different focussing screen. Then, you have a nice "camera", and are ready for serious photographic action.

Apple has introduced the same philosophy with the new iPhone 4 SmartModule. Don't be fooled, it's not a phone, its a module. Because, you need to add a case, and perhaps an earpiece to make it a phone. But, then it's really a crazy-good product.

After living with the iPhone 4 for a little while, I cannot imagine what the heck Apple was thinking about when they placed the antennas where they are. It's a bold, risky move. However, if you had come to AntennaSys and said, "We'd like to put the antennas in the place with the highest probability of being covered with a hand!", I would have sat you down and calmly explored exactly why it is you felt you must do this. The fact is I would have tried to talk you out of it and find a better solution. Either it is genius or just plain dumb. Time will tell.

When I first thought about and later played with the iPhone 4, I didn't see where the problem was hiding. In fact, I wrote about how I held the Primordial iPhone for years with the Vulcan iPhone Pinch in order to avoid blocking the antenna at the bottom of the case. I tried the same techniques with the iPhone 4 and it worked fine. What was the fuss about? Then, I tried the Grip of Death, and could not kill a call in my office; though I recognize we could have killed that call if we were in a marginal area. And, I have ignored data transfer while concentrating on voice calls.

Then, I received my very own iPhone 4. And lived with it. And finally saw the light.

It was a small light, on a dark background. At first it was fuzzy and distant. It grew closer and brighter and....... I finally found my glasses on the nightstand. Oh, yeah, I saw the light. It said, "No Service."

With the iPhone 4, a true VIG (Vulcan iPhone Gripper) won't drop a call due to the antenna placement. But, anyone who uses the phone for... say.... email, or texting, or Googling, will isolate themselves from the cellular world while doing so. This is because it seems impossible to hold the phone vertically in one's left hand (Lefties, please forgive me), while typing with the right index finger, without putting that fat fleshy part of our palm, right below our hyper-evolved opposable thumb, smack dab over the "hot spot" of the stainless-steel-rim-interruption-fed cellular antenna.

No worries, we're adaptable, right? Just rotate the phone to horizontal mode. Hold the phone in your left hand from the top. Not so fast! While calendar, email, texting and contacts will rotate in text-entry mode, some apps won't. Use the Vulcan iPhone Grip while trying to do text entry? That's a sure path to physical therapy.The Data Interaction Grip

The Primordial iPhone did not have this problem. Previously, I alluded to the fact that Apple moved the "antenna action" from the back of the case to the sides of the case. This is the root of the problem. Grab your iPhone. If you don't have one, grab a deck of cards. Now, place a call on your CardDeck5 SmartPhone. Freeze! Where was your hand while dialing, or looking up the number? C'mon, take a look. Was your hand gripping the sides of the case or the back of the case? I am betting that you were gripping the sides of the case, and the back of the case had a little semi-circular air space between it and your palm and fingers. Am I right?

The Semi-Circular AirspaceThis little space is what gave the previous generation iPhones, and many other cell phone designs, a fighting chance to work. The antenna's got to breathe! That little, natural, air space greatly reduced detuning the antenna, but won't do much for attenuating the radiation heading for your hand. But, it is the prevention of detuning the antenna that allows the RF energy to transfer into and out of the antenna in the first place! And with the iPhone 4 antenna placement, especially without a case, we're detuning the antenna every time.

Sure, once a call is established, we switch to the Vulcan iPhone Grip and all is well. But, during a "data interaction" with the iPhone 4, we may be killing the cell antenna. That lower-left break in the band (as we are looking at the screen) is its feedpoint. And we are smothering it in lean, trim, sinewy muscle as strong as steel bands. Or so.

In preparation for testing (the results of which will be reported here), I am off to the Apple Store to pick up an Apple Bumper case for my iPhone 4 SmartModule. Perhaps it will then become a SmartPhone.

As Leo Laporte told me when I appeared on TWiT #255, "You shouldn't need a freaking manual to learn how to hold a phone!"

]]>The iPhone 4 SmartModuleFirst Impressions: iPhone 4Spencer WebbSat, 03 Jul 2010 01:15:38 +0000https://www.antennasys.com/antennasys-blog/2010/7/2/first-impressions-iphone-4.html5b1040cf4611a06de08de662:5b104802af68497d6a4558cb:5b104802af68497d6a4558d8I did not expect to be posting this before my personal iPhone 4 arrived,
but my friend Keith showed up with his shiny-new iPhone 4. We did a quick
test in my office; this is not an exhaustive test, but it's a start.I did not expect to be posting this before my personal iPhone 4 arrived, but my friend Keith showed up with his shiny-new iPhone 4. We did a quick test in my office; this is not an exhaustive test, but it's a start.

First, we placed a call to Paul, another iPhone 4 user. We were going to invoke FaceTime, but I realized that our firewall was too tight - FaceTime requires some ports opened. We'll play with that another time.

The Two-Finger Suspension GripWhile on a live call, we held the phone from the top, and observed five bars. Then, I asked Keith to give the phone a two-handed Grip of Death. After a delay of perhaps fifteen seconds, the signal strength fell to one bar. Regardless of how we applied the Grip of Death, we could not cause the call to drop. I realize this says more about my local signal strength than it does about the phone.

Then, we used electrical tape (white) and wrapped the "band" on the lower half of the phone. Then we repeated the test, again with a live call. The results were identical. There was no discernable difference when we used tape.

Finally, we repeated the test with my Primordial iPhone (a first generation model), and got the same results, except instead of five bars, we started with four bars. Do I think that difference was significant - no, I do not. We still have no idea what the bars mean, especially in the different models.

We did not spend a lot of time, mostly because we were heading for a sushi lunch, but I did draw a couple of preliminary conclusions:

1) The iPhone 4 is not nearly as hypersensitive to "hand" effects as I was being led to believe from the media buzz.

2) The iPhone 4 seems to be as sensitive to hand effects as the Primordial iPhone.

3) Electrical tape over the "band" did nothing.

The Two-Handed Grip of DeathI had predicted in a previous blog posting that the application of electrical tape would not do much, and nothing in this first test implies otherwise. I was frankly surprised that the Grip of Death did not affect the iPhone 4 any more than the primordial iPhone. I was quoted in the press as saying that we're "making a mountain out of a molehill". It may be truer than I thought.

Today Apple released a letter indicating that they were "stunned" to learn that their signal-bar algorithm is "totally wrong", and has been so since the first iPhone models. According to Apple, it was indicating 2 bars more than it should. Further, AT&T has "recently" suggested a standard, and Apple will issue a software patch so that the signal-bar display will conform to this standard.

I've said it before, but now let me say it slightly differently: the only worthy metric for the quality of the cellphone is frequency of dropped calls when compared with other phones used in the same manner, over time. You cannot tell the difference between a "one-bar" conversation with your mother, and a "five-bar" conversation. (This is not be confused with having a conversation with your mother FROM a bar, which I don't recommend.) The only way to observe dropped calls is to use the phone for a statistically significant amount of time.

So, if you are a Bar Watcher, Apple's letter is going to change your observations. If you are a Dropped Call Counter, it will mean nothing. Bar Watching has no value in my opinion; I think it is a waste of your valuable time. If you have a routine that has you driving/walking/riding the same route every weekday, you probably know where your "holes" are. This is how a Dropped Call Counter is going to make observations. Apple's letter does nothing but divert attention from your valuable observations.

My opinion is that it's good that Apple is conforming to a standard. Beyond that.... it's spin.

More details to follow. I will be receiving my iPhone next week.

]]>First Impressions: iPhone 4iPhone 4 Testing Soon, But First...Spencer WebbThu, 01 Jul 2010 02:58:01 +0000https://www.antennasys.com/antennasys-blog/2010/6/30/iphone-4-testing-soon-but-first.html5b1040cf4611a06de08de662:5b104802af68497d6a4558cb:5b104802af68497d6a4558d7Arrrrgh! What to do while you wait? Enjoy Independence Day with your
family. I promise to be back with first hand impressions of the iPhone 4
and its antennas soon.

Arrrrgh! What to do while you wait? Enjoy Independence Day with your family. I promise to be back with first hand impressions of the iPhone 4 and its antennas soon.

The iPhone 4 antenna controversy was way bigger than I realized. The traffic to this site was incredible, and the extent of the blogs and news sites that picked up my comments was humbling. I also did four telephone interviews, including the Wall Street Journal - they asked for photos, so we had some fun. And yes, I did call it the "Vulcan iPhone Pinch". And no, Leonard Nimoy has not called.

I received many emails, too. The overwhelming tone of the email was very friendly; I wish I could respond to all of them immediately, but I am afraid that will have to wait. I will try to touch on the topics raised in some of the emails in this blog entry.

First off, I still don't have my iPhone 4 yet. Sigh. I am waiting patiently, so keep in mind that all my comments are based upon my experience with designing embedded antennas, and not with the specific antennas in question. I promise to post my first-hand experiences here once mine arrives. Also, I don't have any Apple-specific information that you don't have access to. I am not a consultant to Apple, and have never been; I don't even play one on TV. I don't have an axe to grind. Nor an iPhone 4 to play with. But, I digress...

I have seen mention of the electrical tape fix, the scotch tape fix, the bumper case fix, even the short-the-other slot fix on various web sites. The important thing to realize is that we are dealing with radio frequency (RF) currents in the antenna, not direct current (DC) as you will find in a flashlight, for example. If you place a thin insulator (tape) across the "gap" and over the "band" on the iPhone 4, I would not expect that to make a very big difference. With such a thin insulator you are effectively preventing a short at DC (zero Hertz), but at the RF frequencies involved (around 1GHz, or one billion Hertz) you are just making a large capacitor. A capacitor is fundamentally two conducting plates separated by an insulator. When the capacitance is high enough (plates big, insulator thin) at the frequencies in question, it looks just like a short circuit. So, I would not expect tape to create any improvement when the Grip Of Death is used (see photo).

When I was on the phone with the WSJ, I explained the two distinct effects that holding the phone over the antennas will impart: detuning and attenuation.

Detuning can be understood by imagining a wine glass that is empty. If we tap the glass with a fork, the glass will ring, or resonate, at some frequency. If we put some wine in it (or apple cider, since I don't imbibe) the resonant frequency will change and in this case increase. This is the same for antennas. Antennas are generally resonant at their frequencies of operation, and when we put our hand over them we "load" them with the dielectric of our bag of salty water. This lowers the resonant frequency of the antenna and may make it harder to squirt energy into it at the frequency we want. If the antenna is particularly narrow-band, it may "kill" it completely. Generally, physically small (compared to a wavelength) antennas are narrow-band and large antennas may be wide-band. This is why detuning is the first detrimental effect of putting your hand on an antenna. Any antenna.

The second effect is attenuation, or loss. Your hand is a dielectric, meaning it concentrates electric fields more than air. This factor is called the dielectric constant, and for your hand is pretty high, like 12 or 20 or so. It depends on your diet and BMI, so it's kind of personal and I don't want to make anyone uncomfortable by dwelling on it; the important thing is to be healthy. Oh... right.... so this is what detunes the antenna. But, your hand is also conductive, but not perfectly so. So you WILL get a shock if you stick your thumb in a light socket, and I don't recommend it. This not-so-perfect conductor is what we call "lossy". RF energy impinging upon your hand (or head) is partially going to be turned into heat. This is the SAR we were talking about, and you may have heard of. This leads to an attenuation (reduction) in the signal being radiated into space by the antenna. This is the other bad thing that happens to hand-wrapped antennas. Once turned to heat, the RF energy is gone. Just ask your dinner in the microwave.

So, detuning causes problems with squeezing energy from the circuitry into the antenna (or vice versa), and attenuation causes problems with losing energy to heat.

The so-called bumper case is a much thicker insulator (or dielectric) than a piece of tape. It pushes the lossy dielectric (your hand) further away, significantly reducing the capacitance. I would expect this to reduce the detuning effect, but not the attenuating effect. Will it help? You betcha'. However, it is a tradeoff: pushing a very high dielectric constant but lossy material away, and substituting it with a lower dielectric constant material. If I were a betting man, I would guess that the dielectric constant of the materials used is about 3.3. So, it still will load the antenna, but not as much; and it is entirely possible that this was taken into consideration in the design of the antenna. Since I have had a case on my Primordial iPhone since it was new, I expect to do the same with the iPhone 4. When it gets here. Any time now.

Now I want to rant a bit about the "experimental method" people have been using. The iPhone 4 was out for roughly 24 hours before people were publishing the results of "tests" proving that it had inferior performance. At my company, when I get to hook my fancy laboratory gear up to my client's equipment in very controlled circumstances I can't do it that fast. Folks, there are a couple of reasons that you need to give this product some time before jumping to conclusions.

First, we have no earthly idea what those little bars in the upper left corner of our screen really represent, yet we are staring at them like they're going to help us find out what those damn numbers on LOST meant. Steve Gibson of Gibson Research (grc.com) did a great piece on the meaning of the signal bars; I am a huge fan of his, and his measured approach to technical challenges are worthy of our respect. We don't know what the bars mean, beyond more is better and less is ... less better. We also don't have a handle on the time constant of the bars, which is to say we don't know when the bars change with respect to when the signal changes. And worse, we don't know if it's consistent. After all, it's controlled by software.

Secondly, the cellular system is composed of many cell sites. While you are making observations, you have no idea whether your iPhone is staying on one cell site, or switching between several. This will completely obfuscate any measurements, even if you decided that the bars are useful. In the good old days, when cell phones worked on steam, there was usually a service screen you can hack your way to which would show which site you're on, and how strong it was in real engineering terms (dBm). I have never seen that capability on the iPhone (but, I didn't look too hard). Such a capability would be hugely helpful in our experiments.

So, how do we evaluate the performance with these limitations? The answer is: over more time, in more situations. You need to observe more bars in more places. (I know, cheap shot.) Give it a couple of weeks. Use it like you used your last phone. If it doesn't make you happy, return it to Apple. But, give it a chance, and 24 hours ain't it.

Several reporters wrote that I "blame the FCC for the iPhone antenna problems." Well, I did say "it's the FCC's fault", but I was a bit glib. It's the whole process that drives the design (I did say that, too), and part of that process is the tests the phones must pass. And the FCC could care less whether your phone drops your calls in the middle of a conversation or not; they care about protecting the "spectrum" and safety. AT&T does care about efficiency, but they assume your hand is made of styrofoam. Apple cares about striking a balance between product coolness (you'll buy it) and product efficacy (you'll keep it). All of these pressures lead a product to the end point. And then the unpredictable takes over anyway, so enjoy the ride.

So, why didn't Apple do it differently? That's a question I thought about through several showers. I have finally boiled it down to one thing: any performance improvement would have made the iPhone 4 bigger. Period. Apple is putting ten pounds of stuff in a five-pound bag. Put air space around the antenna to make it less sensitive to the presence of the human hand? Fuggetaboutit. Air doesn't sell phones. Gyroscopes, accelerometers, high resolution screens, multiple cellular carrier capability (did I say that?), and big batteries.... that's what the people want.

You just gotta hold it like this.

]]>Hey, Hold the Phone!! (Like this...)Apple iPhone 4 Antennas...Spencer WebbThu, 24 Jun 2010 19:50:30 +0000https://www.antennasys.com/antennasys-blog/2010/6/24/apple-iphone-4-antennas.html5b1040cf4611a06de08de662:5b104802af68497d6a4558cb:5b104802af68497d6a4558d5I received a phone call today from PC Magazine. They were running a story
on the new Apple iPhone 4, specifically the reports (PC Mag, Gizmodo,
Engadget) that people are experiencing decreased reception on their cell
phone when they hold the phone by the metal frame.I received a phone call today from PC Magazine. They were running a story on the new Apple iPhone 4, specifically the reports (PC Mag, Gizmodo, Engadget) that people are experiencing decreased reception on their cell phone when they hold the phone by the metal frame. That frame has been touted by Apple, in the keynote address by Jobs, as being part of the antenna system. Here is a brief summary of what I told the reporter who called me, and a little extra. (The reporter was Mark Hachman, News Editor, PCMag.com/ExtremeTech.com.)

I saw the photo of the frame of the iPhone in the slideshow at the end of Steve Job's keynote address at the Developers Conference. There are three gaps in the stainless steel band which are allegedly part of the antenna system. I have not had a lot of time to analyze their structure, nor do I have one in my hands yet. So, either it is public relations hokum, or those slots are really part of the antenna structure. They do appear to be active, based on observations.

In the first generation iPhone (which I am currently using), the antennas were on the back of the phone, near the bottom. There was a piece of plastic on the bottom covering the antennas, so you knew where they were. I developed a way to hold the phone which avoided covering this area with my hand, similar to the Gizmodo article linked above. It is worth stepping back a moment and asking the question, "Why are the antennas placed where my hand is MOST likely to cover it?" It's a fair question.

The FCC puts strict limits on the amount of energy from a handheld device that may be absorbed by the body. We call this Specific Absorbtion Rate, or SAR. In the olden days, when I walked ten miles to school in three feet of snow, uphill in both directions, cell phones had pull-up antennas. This allowed the designer to use a half-wave antenna variant, and put the point of maximum radiation somewhat away from the user's cranium. Of course, most people did not think it was necessary and kept the antenna stowed. Motorola's flip phone acutally had a second helical antenna that was switched into place when this was the case. But, more importantly, SAR rules were not yet in effect.

Flip phones became yesterday's style, and phones were becoming more monolithic. Some phones, like the early Treo, kept the antenna in the traditional location at the top of the phone, near one edge, but reduced it to a short stub. Whips became stubs, stubs became bumps, and finally antennas were embedded into the rectangular volume of the phone. The trouble was SAR; if you left the antenna at the top, the user was now pressing it into their head, insuring lots of tissue heating. Enter the bottom-located cellphone antenna.

Just about every cell phone in current production has the antenna located at the bottom. This insures that the radiating portion of the antenna is furthest from the head. Apple was not the first to locate the antenna on the bottom, and certainly won't be the last. The problem is that humans have their hands below their ears, so the most natural position for the hand is covering the antenna. This can't be a good design decision, can it? How can we be stuck with this conundrum? It's the FCC's fault.

You see, when the FCC tests are run, the head is required to be in the vicinity of the phone. But, the hand is not!! And the FCC's tests are not the only tests that must be passed by a candidate product. AT&T has their own requirements for devices put on their network, and antenna efficiency is one of them. I know because I have designed quad-band GSM antennas for the AT&T network. The AT&T test similarly does not require the hand to be on the phone.

So, naturally, the design evolved to meet requirements - and efficient transmission and reception while being held by a human hand are simply not design requirements!

OK, back to the iPhone 4. The antenna structure for the cell phone is still down at the bottom (I won't address the WiFi nor GPS antennas in this blog entry). The iPhone 4 has two symmetrical slots in the stainless frame. If you short these slots, or cover them with your hand, the antenna performance will suffer (see this video I found on YouTube). There is no way around this, it's a design compromise that is forced by the requirements of the FCC, AT&T, Apple's marketing department and Apple's industrial designers, to name a few.

One of the questions the intrepid reporter from PC Magazine asked me was, "Will putting the phone in a pocket and using a Bluetooth device help?" Good question. The answer is yes, to a point. The first generation iPhone clearly had a conductive surface below the antenna (I hesitate to call it a ground plane, because it is too small). So, putting it in your pocket with the screen toward your body and the antennas facing out while using your Bluetooth earpiece will work better than holding the phone with your hand. In fact, in my car my iPhone sits forward on the dashboard, under the windshield, screen down while I use my Jawbone. Works great. (However, if you put your iPhone in your left back pocket, and your earpiece in your right ear, you may have issues. This is a failing of the Bluetooth system in dealing with severe body losses at 2.4GHz, not the cellphone's problem.)

The iPhone 4, however, moved the antenna action from the back of the phone to the sides. This probably improves the isotropy of the radiation pattern, but only when the phone is suspended magically in air. Not too helpful. Putting this iPhone 4 in your pocket will likely couple more energy into your body (you bag of salt water, you) than did the first generation model. Yep, I predict it will be worse.

So, what's an iPhone lover to do? Well, I voted with my dollars. I ordered my iPhone 4 to replace my Original. I already know how to do the Vulcan Antenna Grip on the iPhone, and I am wearing out my current model.

And sometimes an antenna that's not great, but good enough, is good enough.

]]>Apple iPhone 4 Antennas...30 dB in 30 Minutes...Spencer WebbMon, 31 May 2010 02:24:47 +0000https://www.antennasys.com/antennasys-blog/2010/5/30/30-db-in-30-minutes.html5b1040cf4611a06de08de662:5b104802af68497d6a4558cb:5b104802af68497d6a4558d4A couple of years ago: the phone rang, and it was another potential client.
A referral from a referral... in any event, they thought they had an
antenna problem. They were right.A couple of years ago: the phone rang, and it was another potential client. A referral from a referral... in any event, they thought they had an antenna problem. They were right.

It seems they were building an interesting on-body medical sensor which included a data transceiver for a clinical application. (If this sounds familiar, it should. These days, I seem to do many projects with "on-body" and "medical" in their descriptions.) This transceiver was at 2.4 GHz, and the size of the device was bigger than a wristwatch, but smaller than a deck of cards; it was powered by a coin cell. It was located on the body of a patient in a hospital ward, and it needed to communicate with a central monitoring station about 25-50 feet away. Presently, it was doing a lousy job of it. Sometimes, they had to lay the receiver on the patient's chest to get the data. This was not only not good, it was not wireless.

I needed to know where the client wanted me to take them. "What is your goal?"

"We need these 25 systems to work for the clinical trials. The hardware is all built, and time is short. It doesn't have to be pretty, but it has to work."

I scheduled a one-day session for them at my lab. At worst, I thought, we'd get to the bottom of the problem and at least know what was going on. At best, we'd solve the problem and know how to modify the built units. I made sure the benches were (sufficiently) cleared off, the spectrum- and network-analyzers were warmed up, and the 'fridge was stocked.

They had built up 25 of these devices for a clinical trial; a sort of beta-test, but with lots of interested parties paying close attention. The issue of way-too-short-range of the data link was not the death knell of their product, because they had really cool sensor technology which was the primary focus. But, it wasn't going to impress anyone either. They wanted the problem solved. Now.

The Senior Engineer on the project showed up at my lab at the appointed time of 10:00am, and we got down to business; we'll call him Joe - not his real name. He brought several of the sensors, complete with extra batteries and spare units I could play with. He also brought their prototype monitoring unit, which had a simple off-the-shelf sleeve-dipole antenna on it. We fired up one of the sensors, and it began transmitting packets of data about once every ten seconds.

Sure enough, the receiver had to be within about two or three feet in order to hear the signal. Not good. I asked Joe lots of questions about how the unit gets deployed in the field, where the receiver would be set up, what the design of the receiver was, and so on. I set up our spectrum analyzer and a calibrated dipole to observe the signal. Man, that was one weak signal. With Joe's permission, I cracked open the case of the unit.

Joe explained that they were using a Chipcon transceiver chip (now TI), and they followed the data sheet's schematic exactly. Further, they made a "loop" antenna following some design equations one of their engineers found in the literature. Hmmm. I looked at the loop of wire, and something was bugging me.

"What was the calculated size of the loop?," I patiently asked.

"I believe it was one-half wavelength," Joe patiently explained.

"Did you say ONE-HALF wavelength?"

"Yessir."

If you see where this is going, congratulations. Joe didn't, and his folks back at the office sure didn't, and that's why he was in my office. I carefully measured the dimensions of the wire antenna they had made and noted it in my lab notebook. It was sort of a fat folded-dipole shape. I took pictures to document everything (a habit of mine that often pays off in 1000-word increments). Then, I opened my toolbox and removed the most powerful weapon I had.

I readied my high-quality wire cutters.

"Joe, watch the spectrum analyzer carefully."

With both his eyes on the screen of the analyzer, and mine split between that screen and the device, I cut the wire right at its midpoint. The formally puny peak on the screen jumped up. A bunch.

"Um, that just went up 30 dB."

"Yessir." It was my turn to savor my favorite moment as a consultant. If Joe smiled any broader, his face was gonna break.

"OK... what's going on??!", Joe asked. It was 10:30am.

I explained that somebody's slide rule slipped. If you make a loop of wire, and I don't care what shape, with one half-wavelength of wire, it's going to look like a shorted quarterwave transmission line, and very close to an open-circuit. If it was going to be a loop, it should have been smaller and resonated with a capacitor, or longer and about one-wavelength long. It was about as perfectly wrong as it could have been. Snipping the wire at the center point essentially made it a dipole, with each leg folded back on itself. Probably not very efficient, and probably not well impedance-matched, but... 30 dB better than what they had.

I showed him how to open each unit, snip the wire, tape the ends in place and get on with their clinical trial. He left a happy engineer. The clinical trial was a success, their product worked, and life was good.

After the clinical trials, I was invited to redesign their PC board, and put a custom antenna on it. We ended up designing a cool embedded antenna which used the PC board copper and ZERO matching components. If memory serves, we eliminated somewhere between four and six components. The new antenna was designed and optimized using our CST Microwave Studio tools. We optimized the antenna in situ, taking into account the battery, PC board, housing and the human body. Performance was excellent; it worked just as envisioned in the clinical environment.

With much gratitude, I can report that we are still working with this happy customer.

Sometimes, you win the game by making base hits and hustling in the outfield. You fight for every inch. But, sometimes, just occasionally, with the bases loaded and the wind blowing in the right direction... you get 30 dB in 30 minutes.